But in my experience it can result in broken downloads; http error codes seem to cascade or something. It should be safe enough if you are talking to apt-cacher-ng (either mirror mode or proxy mode). Otherwise, be prepared to disable it if your mirror breaks.

I would advise against setting languages to none, because it breaks apt-cache search (none means none, when useful searches would need descriptions in at least one language). The locale-based default includes unnecessary regional variants, but something like this: